The present invention relates to bearings for timepieces, more particularly of the type allowing shocks to be absorbed. The constructors of mechanical watches have, for a long time, been designing numerous devices which allow a staff to absorb the energy resulting from a shock, in particular a lateral shock, by abutment against a wall of the hole of the base block which it traverses, whilst allowing a momentary displacement of the small rod before it is returned to its lock position under the action of a spring.
FIGS. 1 and 2 illustrate a device termed inverted double cone which is currently used in timepieces found on the market.
A support 1, the base of which comprises a hole 2 for the passage of the balance staff 3 ended by a small rod 3a, makes it possible to position a jewelled bearing 20 in which there are immobilised a pierced stone 4 traversed by the small rod 3a and a counter-pivot stone 5. The jewelled bearing 20 is retained in a housing 6 of the support 1 by a spring 10 which, in this example, comprises radial extensions 9 which compress the counter-pivot stone 5. The housing 6 comprises two bearing surfaces 7, 7a in the form of inverted cones on which the complementary bearing surfaces 8, 8a of the jewelled bearing 20 are supported, said bearing surfaces requiring to be produced with very great precision. In the case of an axial shock, the pierced stone 4, the counter-pivot stone 5 and the balance staff are displaced and the spring 10 acts alone to return the balance staff 3 into its initial position. The spring 10 is dimensioned to have a displacement limit so that, beyond this limit, the balance staff 3 comes into contact with stops 14 making it possible for said staff 3 to absorb the shock, which the small rods 3a of the staff 3 cannot do without the risk of breaking. In the case of lateral shock, i.e. when the end of the small rod unbalances the jewelled bearing 20 out of its lock plane, the spring 10 cooperates with the complementary inclined planes 7, 7a; 8, 8a in order to re-centre the jewelled bearing 20. Such bearings have been sold for example under the trademark Incabloc®. These springs can be produced in chromium-cobalt alloy or brass and are manufactured by traditional cutting means.
Now, a disadvantage of these shock-absorber bearings is that they are dismantlable. In fact, it is intended that these shock-absorber bearings are able to be dismantled for servicing operations after sale and maintenance. Shock-absorber bearings are therefore obtained, the assembly of which is not easy. Effectively, some parts, such as the support 1 and the spring 10, must be orientated and manipulated in a certain manner during the assembly operation in order to assemble the shock-absorber bearing. Consequently, not only are the constituent parts of the shock-absorber bearing complex but furthermore total automation of the assembly is not possible and makes said shock-absorber bearing more expensive.